Preparation of oil-soluble lead soaps from petroleum oxidates as lubricant additives



United States Patent Ofiice PREPARATION OF OIL-SOLUBLE LEAD SOAPS FROM PETROLEUM OXIDATES AS LUBRICANT ADDITIVES Edward R. Christensen, Beacon,

Texaco Inc., a corporation No Drawing. Filed Aug. 16, 1956, Ser. No. 604,303 6 Claims. (Cl. 260-'414) N .Y., assignor to of Delaware This invention relates to a new class of extreme pressure additives for lubricating compositions. More pardate fractions of various types as the saponifiable ma-- teri'al have been unsuccessful because of the insolubility in lubricating oils of the lead oxidate soaps.

It has now been found that lead soaps which are unexpectedly very much superior in oil solubility and other properties to lead oxidate soaps which have beenprepared heretofore; are obtained by employing as the saponifiable material of a hydrocarbon solvent from a petroleum oxidate obtained by carrying out a limited oxidation upon a refined lubricating oil of low wax content. The lead soaps prepared from such oxidate fractions form stable lubricating oil compositions containing over 1 percent by weight of dissolved lead, having extreme pressure properties which are equivalent or even superior to those obtainable with lead naphthenate.

The lubricating oils from which the oxidates are prepared are refined mineral oils in the ordinary lubricating oil viscosity range, suchas from about 75 seconds Saybolt Universal at 100 F, to about 225 seconds Saybolt Universal at 210 F., obtained either from low wax content crudes or from parafiinic crudes'which have been dewaxed down to a pour point below about 5 F. They are refined by the usual methods employed to remove aromatic ,and asphaltic compounds, including solvent refining and, propane deasphalting of residual oils. The preferred oils for this purpose are .oils in the viscosity range from about 75m about 600 seconds Saybolt Universal at 100 F., having pour points below about 0 F. Particularly suitable oils are those in the viscosity range from about 90 100 F.

The oxidation process is carried out in the known manner by blowing air through the lubricating oil at an elevated temperature, such as a temperature above about 250 F. The reaction is preferably carried out at temperatures in about the range 270-330 F. and at atmospheric or moderately elevated pressures, such as pressures up to about 200 p.s.i.g., employing air rates of about 15-35 standard cubic feet of air per hour per pound of charge. A catalyst, such manganate or potassium stearate may be present if desired. The oxidation is carried out until the product has a neutralization number of about 25400 and a saponian oxidate fraction extracted by means.

fication number of about and a saponification number of about 100-150.

The petroleum oxidate extracted with a hydrocarbon solvent such as benzene or a petroleum distillate fraction boiling in about the range 100300 F. The preferred solvent is a parafiinic hydrocarbon or predominantly paraifinic hydrocarbon mixture, comprising chiefly C -C paraffins. The solvent extraction may be carried out at ordinary temperatures or at slightly elevated temperatures, employing various proportions of oxidate date-solvent ratios from about 1:1 to about 1:4. 1

The conversion of the separated saponifiable material into the lead soap may be carried out by any convenient method, as for example by distilling off the solvent and treating the saponifiable material with litharge. Since this reaction takes place only slowly, the conversion to the lead soap is more conveniently carried out by first saponifying with an alkali metal hydroxide and then converting the alkali metal soap to the lead soap by acidifying an aqueous solution of the soap with an inorganic acid and treating the. recovered organic acids with lead oxide, or by treating the'alkali metal soap in aqueoussolution with a water soluble lead salt, such as lead acetate. if desired by extraction of the soap with a hydrocarbon solvent such as naphtha or benzene. According to the preferred method, the hydrocarbon solvent containing the dissolved oxidate fraction is extracted with an aqueous solution containing sufiicient alkali metal hydroxide to saponify all of the saponifiable material, and the aquefromthe hydrocar bon solvent which about 1.5 percent of to about 400 seconds Saybolt Universal at a as potassium pera ous solution of alkali metal soap obtained. is separated contains the unsaponifiable material: a f r The lead soaps of this inventionmaybe employed in They are'preferably employed in gear oils in amounts percent'by weight, or sufficient to a of at least about 5 give at least about 1 percent, and preferably at least The lubricant compositions wherein these soaps are from crudes of various types or synthetic oils by any of the conventional refining methods. Other compounding ingredients may also be present in the composition, such as pour point depressors, oiliness agents, corrosion inhibitors, anti-oxidants, extreme pressure agents of various types, viscosity improving agents and thickening agents such as soaps either in minor amounts or in grease-forming proportions. Additives of the active sulfur type,

benzyl disulfide, etc., in lubricant compositions in conjunction with the lead soaps.

The following examples are given for the purpose of more fully disclosing the invention.

EXAMPLE I A petroleum oxidate'was' prepared by oxidizing a lubricating oil fraction which acid treated pressed distillate from a paratlin base crude.

Typical tests on this oil are as follows.

Gravity, API 32.4 Flash, COC, F. 340 Fire, Cleve., F. 400 Viscosity, SUS at 100 F. 82.9 V.I. Pour, F.

Patented Apr. 4,

obtained as described above is i and solvent, preferably With oXi- Unsaponifiable matter may be removed 1 dissolved lead in the composition.

fatty oils or hydrocarbon oils, di--' are very advantageously employed was an Edeleanu refined and Composition:

Aromatic carbon atoms, percent 22.8 Naphthenic carbon atoms, percent Alkyl carbon atoms, percent 77.2

The oxidation was carried out by passing air through the charge in an aluminum reactor at a rate of 20 cubic feet per hour per pound of charge for about 2 hours, while the charge was maintained at 270 F. and under 65 p.s.i.g. pressure. The oxidation product obtained had a neutralization number of 70.4, a saponification number of 146 and a non-saponifiable content of 45.6 percent.

A lead soap was prepared from this oxidate in the following manner. A 100 gram .sample of oxidate was saponified with 16 grams of KOH in aqueous solution and the unsaponifiables extracted with 250 ml. of precipitation naphtha, which is a hydrocarbon fraction com prising chiefly hexanes and having an end boiling point of about 200 F. The aqueous solution was acidified to litmus paper with hydrochloric acid and the recovered organic acids were extracted with 250 ml. of benzene. The benzene solution containing the acids was separated from the aqueous solution and the benzene removed by distillation. A 25 gram sample of the acids was treated with an aqueous solution containing 16 grams of lead acetate, and the lead soap which precipitated out wasfiltered off and washed with benzene. A saturated oil solution of the lead soap was prepared by heating 4 grams of the soap with 50 ml. (about 42 grams) of a refined paraffinic distillate oil having a viscosity of 165 seconds Saybolt Universal at 100 F. The mixture was heated on a steam .bath for 8 hours, cooled overnight and filtered.

The following tests were obtained upon the oxidate acids separated by the saponification procedure and upon the oil blend containing the lead soap.

Recovered acids:

The test for naphthenic acids employed was a colorimetric test based upon the pentane solubility of the copper soap. The test is carried out by saponifying a small sample of the acid and mildly oxidizing the soap with permanganate in order to destroy unsaturated acids. The excess permanganate is destroyed with sodium thiosulfate and insoluble inorganic salts removed by filtration. A sample of the filtrate is treated with excess aqueous copper sulfate solution and the precipitated copper soap separated, dried and tested by comparing a pentane solution of the soap with color standards containing known amounts of copper naphthenate in pentane solution.

EXAMPLE II A 200 gram sample of the oxidate of Example I was extracted with 200 ml. of precipitation naphtha at room temperature and the insoluble material separated. The naphtha solution was extracted with excess 10 percent KOH solution, the aqueous alkaline layer separated and made acid to litmus paper with hydrochloric acid and the recovered organic acids extracted with ether. The separated acids were converted to the lead soap by treating them with 42 grams of lead acetate dissolved in water. The lead soap obtained was blended with paraffinic 16S viscosity lubricating oil to form a saturated solution as described in Example I.

The following tests were obtained upon the separated acids and upon the oil blend.

Recovered acids:

Wt. percent 39.0 Neutralization No. 111 Saponification No.

5 Lead content of soap, percent, calculated 21.1 Lead content of blend, percent, found 0.18 Solubility of lead soap, percent, calculated 0.9

EXAMPLE III A petroleum oxidate was prepared from an oil of substantially the same type as that employed in Example I except that it was dewaxed to a low wax content. This oil was a wax distillate from a paraffin base crude which 15 was furfural refined, clay and acid treated, and solvent dewaxed. Typical tests upon this oil are as follows.

described in Example I. The oxidate obtained had a neutralization number of 69, a saponification number of 142 and contained 41.6 percent of unsaponifiables.

The saponifiable material was separated from a portion of the oxidate by saponification with aqueous KOH solution and this material was converted into the lead soap and a saturated blend of the lead soap in lubricating oil prepared as described in Example I. The following tests were obtained upon the separated saponifiable material and upon saturated oil blend of the lead soap.

Recovered acids:

Wt. percent 54.5 Neutralization No. 108 Saponification No. 142 Naphthenic acids Trace Lead content of soap, percent, calculated 20.1 Lead content of blend, percent, found 0.34 Solubility of lead soap, percent, calculated 1.7

A lead soap was prepared from another portion of the oxidate described in Example III by carrying out a naphtha extraction step before the saponification. The method in detail was as follow: A 500 gram portion of the oxidate was stirred with one liter of precipitation naphtha at 60 C., the mixture allowed to cool to 25 C. and naphtha decanted. This process was repeated with four 200 ml. portions of the naphtha. The naphtha extracts were combined, allowed to stand overnight and the naphtha decanted from the small amount of insoluble material. A 200 ml. sample of the naphtha extract was removed for testing and the remainder of the naph- 65 tha solution was extracted with 500 ml. of 10 percent sodium hydroxide solution in two successive extraction steps. The alkali extract obtained was neutralized with hydrochloric acid, made slightly basic with sodium hydroxide and treated with 58 grams of lead acetate in aqueous solution. The lead soap formed was extracted with naphtha and the naphtha evaporated by heating to C.

A saturated oil blend of the lead soap was obtained by heating a mixture of 51 grams of the lead soap and 400 75 grams of the viscosity parafiin base lubricating oil to cooling to room temperature Lead content of blend, percent, found 2.02 Solubility of lead soap, percent, calculated 10.74 EXAMPLE v A petroleum oxidate Was prepared by oxidizing lubricating oil of a diiferent type. This was an Edeleanu refined and acid treated distillate fraction from an naphthene base crude. Typical tests upon this oil are as follows: Gravity, API 26.7 Flash, COC, F. 325 Fire, Cleve., F. .365 Viscosity, SUS at 100 F. 99.6 V.I. 25 Pour, F. -45 Composition:

Aromatic carbon atoms, percent 18.9

Naphthenic carbon atoms, percent 28.6

Alkyl carbon atoms, percent 52.4

The oxidation was carried out as described in Example I. The oxidate obtained had a neutralization number of 49, a Saponification number of 102 and contained 56.9 percent of unsaponifiables.

The saponifiable material was separated from a 5 tion of the oxidate by Saponification with aqueous KOH solution and this material was converted into the lead soap and a saturated blend of the lead soap in lubricating oil prepared as described in Example I. The following tests were obtained: Recovered acids:

Wt. percent 22.0 Neutralization No. 123 Saponification No. 153 Naphthenic acids 0 Lead content of soap, percent, calculated 14.5 Lead content of blend, percent, found 0.13 Solubility of lead soap, percent, calculated 0.9

EXAMPLE VI A lead soap was prepared from another portion of the oxidate described in Example V by the method involving carrying out a prior extraction of the saponifiable material With naphtha. The method employed was as follows: A 500 gram sample of the oxidate was stirred with one liter of precipitation naphtha at 60 C., the mixture allowed to cool to C. and the naphtha decanted. The process was repeated with one 300 ml. portion of the naphtha. The naphtha extracts were combined, allowed to stand overnight, and the naphtha decanted from the small amount of the insoluble material. A 200 ml. sample of the naphtha extract was removed for testing, and the remainder of the naphtha solution was extracted with an aqueous solution containing 45 grams of sodium hydroxide. The alkaline solution was neutralized with acid, made slightly basic with sodium hydroxide and treated with a water solution containing 50 grams of lead acetate. The lead soap formed was extracted with naphtha and the naphtha evaporated off.

A saturated oil blend of the lead soap was formed by heating 137 grams of the lead soap and 450 grams of the 165 viscosity paraffinic lubricating oil at 70-80" C. for 6-7 hours and filtering.

Naphtha extract:

Neutralization No. 31.2 Saponification No 64.6 Lead content of soap, percent, calculated 18.97 Lead content of blend, percent, found 1.72 Solubility of lead soap, percent, calculated 9.05

s show bath x m es-l a s ar of l is is t i oil'f solubility were obtained from petroleum oxidatesTby manner by saponification with contrast with these results, solubility were obtained from the saponifiable materials extracted by means of the hydrocarbon solvent from.

lightly oxidized refined distillate oils of low wax' content, as shown by Examples 'IV and VI.

Table I shows the load carrying properties of the lubricating compositions of Examples IV and VI in the Mean Hertz Load test, as compared with those of the base oil alone and of the base oil containinga commercial lead naphthenate.

Naval Engineering Experiment Station Report on Cooperative Evaluation of ER lubricants, May 3, 1946. The test machine comprises a system of four steel balls, three of which are in contact with each other in one plane in a fixed triangular position in a reservoir containing the oil sample, and a fourth ball above and in contact with the other three. In carrying out the test, the upper ball is rotated While it is pressed against the lower three at any desired pressure by means of a suitable weight applied to a lever arm, and the diameters of the scars on the three lower balls are measured by means of a low power microscope. Load determination is made by comparing the worn spots obtained in 20 to 27 ten-second runs at increasing loads up to welding with those obtained with a theoretically perfect lubricant, and applying a factor.

The above table shows that lead soaps prepared in accordance with this invention were fully equivalent or even superior to lead naphthenate in the extreme pressure properties which they imparted to a mineral lubricating oil.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. The method of making an oil soluble lead soap which comprises oxidizing a refined mineral lubricating oil having a pour point below about 5 F. to a neutralization number in about the range 25-100 and a saponification number in about the range 75-200, extracting a saponifiable material from the oxidized oil with a hydrocarbon solvent, separating the insoluble material, and converting the saponifiable material dissolved in the said solvent into the lead soap.

2. The method according to claim 1 wherein the mineral oil employed in the oxidation step is an oil This test is carried out withthe v so-called Four-Ball E.P. Machine described in the US.

The Mean Hertz drocarbon solvent is a fraction boilingzin about therange 5. T 1 1e methodiaccording the extracted saponifiable material isv saponified with .analkali metal hydroxide, and tbealkali metal soap obtained by the saponificationis converted to the lead soap by treating it in aqueous solution with a water soluble lead salt. I

6. The method of making an oil soluble lead soap which comprises oxidizinga solvent refined distillate oil having a viscosity inabout the range 90-400 seconds Saybolt Universal at, 10011. and. a pour point below about 0? F.1d a neutralization number of about 30-80 and a saponification number of about 100-150, extracting the resulting oxidized oil with a hydrocarbon solvent having an end boiling point of about 200 F. and comprising chiefly hexanes, separating the insoluble material,

and converting the saponifiable material dissolved in the said hydrocarbon solvent into the lead soap by extract ing .the solvent solution with an aqueous solution 'of alkali metal hydroxide, separating the hydrocarbon solvent containing the unsaponifiable material and treating the aqueous solution of alkali metal soap thus obtained with an aqueous solution of lead acetate.

References Cited in the file of this patent UNITED STATES PATENTS 2,218,618 McNab et al. Oct. 22, 1940 2,391,236 Hirsch 18, 1945 2,395,307 Weber et a1 Feb. 19, 1946 2,466,925 Brauner Apr. 12, 1949 2,622,092 Kozacik Dec. 16, 1952 2,669,543 Hirsch Feb. 16, 1954 

1. THE METHOD OF MAKING AN OIL SOLUBLE LEAD SOAP WHICH COMPRISES OXIDIZING A REFINED MINERAL LUBRICATING OIL HAVING A POUR PINT BELOW ABOUT 5*F. TO A NEUTRALIZATION NUMBER IN ABOUT THE RANGE 25-100 AND A SAPONIFICATION NUMBER IN ABOUT THE RANGE 75-200, EXTRACTING A SAPONIFIABLE MATERIAL FROM THE OXIDIZED OIL WITH A HYROCARBON SOLVENT, SEPARATING THE INSOLUBLE MATERIAL, AND CONVERTING THE SAPONIFIABLE MATERIAL DISSOLVED IN THE SAID SOLVENT INTO THE LEAD SOAP. 